Radial seals of rotary engines



June 1968 G. DE COYE DE CASTELET 3,387,539

RADIAL SEALS OF ROTARY ENGINES Filed NOV. 7, 1966 United States Patent3,387,539 RADIAL SEALS 0F ROTARY ENGINES Gatan de Coye dc Castelet,Billancourt, France, assignor to Regie Nationale des Usines Renault,Billancourt,

France Filed Nov. 7, 1966, Ser. No. 592,436 Claims priority, applicationFrance, Nov. 25, 1965, 39,841, Patent 1,464,875 3 Claims. (Cl. 91-56)This invention relates to rotary engines of the type comprising a rotorhaving 2N lobes, an epicycloidal contour, and revolving eccentricalllyin a stator of conjugate contour having (2N +1) lobes.

This type of engine comprises (2N+1) variable volume working chambersformed between the inner contour of the stator on the one hand and theouter contour of the rotor on the other hand.

The necessary fluid-tightness between two adjacent working chambers isobtained by means of radial sealing strips fitted in grooves formed inthe stator along the apex lines whereat two adjacent lobes merge intoeach other, these sealing strips resiliently engaging the epicycloidalcontour of the rotor along a generatrix thereof.

These sealing strips have mostly a rectangular crosssectional contourand are urged against the rotor both by the springs usually associatedwith these strips and by the gas pressure exerted on the edges of thesestrips which are opposite to their bearing surfaces.

However, the operation of these sealing strips is not alwayssatisfactory for their possibility of movement in their guide grooves isattended by substantial variations and is sometimes inadequate to keepthem in sealing contact with the rotor.

Radial sealing strips are also known which operate by pivoting insteadof sliding and are therefore free of the above-mentioned inconveniences.

This invention is concerned with pivoting sealing strips of the typebroadly set forth hereinabove, which have a cross-sectional contour suchthat the frictional force developed by its contact with the rotorrevolving in its normal direction of rotation cannot cause the strips tojam since on the contrary it tends to unwedge them.

This invention is also remarkable in that the gas pressure exerted onthese sealing strips urges these strips against their cylindricalrecess, the rotational torque exerted by the gas pressure being null ornegligible.

In order to afford a clearer understanding of this in vention and of themanner in which the same may be carried out in practice, reference willnow be made to the accompanying drawing illustrating diagrammatically byway of example a typical form of embodiment of a radial sealing stripconstructed according to the teachings of this invention. In thedrawing:

FIGURE 1 is a diagrammatic cross-sectional view of a rotary engine ofthe type referred to herein;

FIGURE 2 is a cross-sectional view showing on a larger scale a radialsealing strip according to this invention, and

FIGURE 3 is a detail view of the strip contour.

Referring first to FIGURE 1, a rotary engine is shown diagrammaticallytherein which comprises a five-lobed stator 1 having mounted therein foreccentric rotation a four-lobed rotor 2. The necessary fluid-tightnessbetween adjacent working chambers such as 1 and 2 is obtained by meansof radial sealing strips 3 fitted in guide grooves formed in the statoralong the apex lines separating adjacent lobes, these sealing stripsresiliently engaging the epicycloidal contour of the rotor 2 along ageneratrix thereof.

3,387,539 Patented June 11, 1968 FIGURE 2 illustrates on a considerablyenlarged scale one of these radial sealing strips, the referencenumerals 1 and 2 designating the engine stator and rotor, respectively,the rotor revolving in the direction of the arrow and being adaptedduring its eccentric rotation to assume the two endmost positions shownby the lines 2 and 2 respectively with respect to the stator.

The radial sealing strip 3 according to the present invention is ofsubstantially cylindrical configuration and mounted with a very smallclearance in a cylindrical recess 4 having a diameter d and its centeraxis 0 is parallel to the apex line whereat two adjacent lobes 1 and 1of the stator (denoted by the point P) but somewhat offset in relationto this point F in a direction opposite to the direction of rotation ofthe rotor. v

The strip portion providing the desired fluid-tightness by engaging therotor contour, as already known per se, is a portion AB of a circlecentered at P and having a radius R, this radius R being the oneselected for tracing the epicycloidal contour of the rotor which istangent to the points A and B in the endmost positions 2 and 2 of therotor, said arc AB, according to a specific feature of this inventionbeing disposed on either side of the circle centered at 0 whereby bothpoints A and B are as close as possible to this center as shown indetail in FIGURE 3, under these conditions the rotational torque exertedby the gas pressure on the sealing strip is of zero or negligible value.

The aforesaid arc AB extnds on either side to points A and B to take dueaccount of plays and thermal expansion.

The relative positions of centers P and 0 must be such that an extensionof radius B P will always be on the right-hand side of center 0, in thecase illustrated in the figure.

Thus, the frictional force produced at the point of contact between therotor and the sealing strip, in a direction inclined to the normal atthis point and in the direction of motion by a certain anglecorresponding to the coeflicient of friction will always be directed tothe right of center 0 and will therefore tend to rotate the strip in thedirection to unwedge same.

The cross-sectional contour of the sealing strip 3 further comprises onthe left-hand side of the figure a backed-off surface A C this point Cbeing selected to permit the pivoting of strip 3 about the center axis 0without causing this point C to interfere with the rotor 2 in theendmost position 2 thereof.

Similarly, on the right-hand side the strip 3 has a backed-01f face B'DE to avoid any contact thereof with the stator 1 during its rotation.

The sealing strip 3 is urged against the rotor 2 by a spring 5 engaginga recessed flat face MN of the strip through the medium of a cup 6having a domed stripengaging face.

Each strip 3 comprises a plurality of springs 5 (not shown) received inholes 7 formed in the stator 1, the axis xy of each hole being offset asmuch as possible to the right with respect to the axis C, whereby thesprings 5 will tend to rotate the strip about the axis 0 in a directionopposite to that in which the rotor normally tends to rotate this strip.

The sealing strip 3 is made of self-lubricating material and if desiredlubricating oil may be fed thereto through an oil duct 8 opening intoits lower portion of groove 4.

As already known in the art the sealing strip 3 is divided into sectionsof adequate length in the longitudinal direction of the guide groove 4.

This radial sealing strip operates as follows:

During its rotational motion the rotor 2 is constantly 3 tangent to thestrip 3 at a point normally lying between A and B.

Theoretically, if all the engine components were geometrically perfect,and if no distortion or wear occurred during the engine operation, thestrip would be relatively motionless.

Actually a certain degree of distortion and play cannot be avoided andthe strip is oscillated about the center axis 0. If the rotor departssomewhat away from its theoretical position the sealing strip is causedto move angularly in the counter-clockwise direction in the caseillustrated, and if the rotor moves towards the strip the latter pivotsin the opposite direction whereby the contact with the rotor isconstantly maintained to the benefit of a highly reliablefluid-tightness between the two adjacent Working chambers.

Of course, various modifications can be made both in the strip structureand in the instrumentalities and mounting means used therefor, and it iscontemplated in the appended claims to cover any such modifications asfall within the true spirit and scope of the invention.

Iclaim:

1. Radial sealing strips for rotary engines of the type comprising arotor having N lobes of epicycloidal contour revolving eccentrically ina stator of conjugate contour with (ZN-H) lobes, said strips beingpivotally mounted in grooves of substantially circular cross-sectionalconfiguration which are formed in the stator parallel to and in closevicinity of the apex lines along which two adjacent lobes merge intoeach other, said strips being resiliently urged against the epicycloidalcontour of the rotor along a generatrix thereof and characterised bytheir novel shape defined as follows:

said strips comprise a portion bearing on the stator which comprise afirst circular are having substantially the same radius as the groove,and another portion bearing against the rotor which has the shape of asecond circular arc having its center ottset in relation to the centerof said first circular arc by a distance such that all the extensions ofthe radiuses of said second circular arc lie on one side of the centerof said second circular arc with respect to the center of said firstcircular are, said second circular are being so positioned that itsendmost points are as close as possible to, and on either side of, saidfirst circular arc.

2. Sealing strip according to claim 1, wherein said second circular arcextends on either side of its theoretically endmost points to take dueaccount of clearances and thermal expansions, said strip contourcomprising on either side between the two circular arcs backed-offportions enabling the strip to oscillate without interfering with therotor on the one hand and the stator on the other hand.

3. The sealing strip according to claim 1 further comprises on the firstcircular are a clearance engageable by a spring, said spring actingalong an axis as remote as possible from the first circular arc andbeing so positioned that its action constantly tends to counteract therotation of said strip by said rotor.

References Cited UNITED STATES PATENTS 12/1965 Toyoda et al 230- 11/1966Linder 230-145

1. RADIAL SEALING STRIPS FOR ROTARY ENGINES OF THE TYPE COMPRISING AROTOR HAVING N LOBES OF EPICYCLOIDAL CONTOUR REVOLVING ECCENTRICALLY INA STATOR OF CONJUGATE CONTOUR WITH (2N+1) LOBES, SAID STRIPS BEINGPIVOTALLY MOUNTED IN GROOVES OF SUBSTANTIALLY CIRCULAR CROSS-SECTIONALCONFIGURATION WHICH ARE FORMED IN THE STATOR PARALLEL TO AND IN CLOSEVICINITY OF THE APEX LINES ALONG WHICH TWO ADJACENT LOBES MERGE INTOEACH OTHER, SAID STRIPS BEING RESILIENTLY URGED AGAINST THE EPICYCLOIDALCONTOUR OF THE ROTOR ALONG A GENERATRIX THEREOF AND CHARACTERISED BYTHEIR NOVEL SHAPE DEFINED AS FOLLOWS: SAID STRIPS COMPRISE A PORTIONBEARING ON THE STATOR WHICH COMPRISES A FIRST CIRCULAR ARC HAVINGSUBSTANTIALLY THE SAME RADIUS AS THE GROOVE, AND ANOTHER